Only two HP-15s were built. The original design called for a wing
with an extreme aspect ratio of 33 to 1. As a result of Dick Schreder
placing 65th in the US Nationals both '15s have been re-winged. The prototype
now has a HP-16 wing and N124MD sports a HP-18 wing.

The HP-15 fuselage is very similar to the HP-14 except that the 1-inch
square-steel-tubing cockpit framing has been replaced by aluminum tubing.
The cockpit is large enough to provide adequate room for a 6' 4"
pilot. As you can see in the pictures below, N124MD's "V" tail
has been replace with a "T" tail from a SGS 1-35 and a tail
wheel from an LS-1. Instruments include three varios (a PZL mechanical;
a ILEC SB7 electric and a RICO electric) as well as a compass, altimeter,
air speed indicator, oxygen flow indicator and Terra Bertea 360 radio.